1 Field of the Invention
The invention relates to a bobbin; in particular, the invention relates to a bobbin for a transformer.
2 Description of the Related Art
A conventional bobbin 10 for a transformer is shown in FIG. 1a and FIG. 1b. The bobbin 10 comprises a body 20, a first partition wall 30a and a plurality of second partition walls 30b. The body 20 receives a bar core (not shown). A wire (not shown) fills the body 20. The body 20, the bar core and the wire constitute the transformer. The first partition wall 30a and the second partition walls 30b are formed on the body 20. The body 20 is divided into a primary side 21 and a secondary side 22 by the first partition wall 30a. The wire comprises a first wire (not shown), filling the primary side 21 of the body 20, and a second wire 60 filling the secondary side 22 of the body 20.
Referring to FIG. 1a and FIG. 1b, the body 20 is provided with a plurality of winding grooves 34, separated by the second partition walls 30b, on the secondary side 22. Each of the second partition walls 30b is provided with a wire-guiding breach 31 and a protrusion 33, as shown in FIG. 1a, or a notch 35 as shown in FIG. 1b. It is noted that all of the protrusions 33 are arranged in line, on the same side and the same level. Also, all of the notches 35 are arranged in line, on the same side and the same level.
A plurality of pins 50 are disposed on the secondary side 22 of the body 20. One of the pins 50 is used as a starting terminal 50a, and one of the pins 50 is used as an ending terminal 50b. The starting end of the second wire 60 attaches to the starting terminal 50a, and the terminal end of the second wire 60 attaches to the ending terminal 50b. Between the second wire 60 attached to starting terminal 50a and the second wire 60 attached to ending terminal 50b, the second wire 60 fills the grooves 34 of the body 20 to form a winding (not shown). After the number of windings located in one of the grooves 34, reaches a set number, the second wire 60 enters the next groove 34 through the breach 31 to continue the winding. Thus, a transformer with variable voltage is formed. To simplify the drawings, FIG. 1a and FIG. 1b simply show the second wire 60 adjacent to the starting terminal 50a and the ending terminal 50b, and the second wire filling the grooves is omitted.
After the second wire fills the grooves and forms a winding, the terminal end of the second wire is far from the ending terminal 50b. It is very dangerous to attach the terminal end of the second wire 60 to the ending terminal 50b without any support. When the terminal end of the second wire 60, far from the ending terminal 50b, is attached to the ending terminal 50b without any support, the second wire 60 is liable to be broken. In addition, the second wire 60, adjacent to the ending terminal 50b, is near the outmost portion of the winding that has the highest voltage. Thus, even though the second wire 60 is not broken, this portion of the second wire 60 is likely to experience short circuit due to its contact with the highest voltage of the winding resulted from undesired displacement.
To solve the above problems, various designs have been provided. In one of these designs, the second wire 60 is additionally twisted before it is attached to the ending terminal 50b. By twisting, the strength of the second wire 60 increases so as to avoid breaking. However, this design requires an additional twisting step, and still cannot properly hold the second wire 60.
Alternatively, in another design as shown in FIG. 1a and FIG. 1b, the second wire 60 can be held by the protrusions 33, or the second wire 60 can be supported by the notches 35. While the notches 35 can support the second wire 60 in certain circumstances, they cannot fix the second wire 60 securely. For instance, the notches 35 can simply prevent the displacement of the second wire 60 resulting from the external force along an arrow X1 in FIG. 1b, but they cannot prevent the displacement of the second wire 60 resulted from the external force along an arrow X2 in FIG. 1b. The protrusions 33 may hold the second wire 60, but they cannot fix the second wire 60 properly.
In order to address the disadvantages of the aforementioned bobbin, the invention provides a bobbin that can fix a wire properly without twisting the wire.
Accordingly, the bobbin of this invention comprises a body, a first partition wall, a second partition wall, at least one third partition wall, and two first pins. The first partition wall, having a first protrusion, is formed on the body. The body is divided into a primary side and a secondary side by the first partition wall. The second partition wall, having a second protrusion with a neck portion, is formed on the secondary side of the body. The third partition wall, having a third protrusion with a notch, is formed on the secondary side of the body so that the third partition wall is close to the second partition wall and away from the first partition wall. The first pins are disposed on the secondary side of the body in a substantially U-shape.
Furthermore, the second partition wall is provided with two first breaches. The third partition wall is provided with two second breaches corresponding to the first breaches respectively. Each of the second breaches is aligned with the corresponding first breach respectively.
Furthermore, the body is provided with two slots adjacent to the first pins respectively. The third protrusion has a first surface, the neck portion has a second surface, and the first surface is flush with the second surface.
Furthermore, each of the first pins is provided with a first arm, a second arm and a connecting section connecting the first arm and the second arm, and the connecting section is disposed outside the body. The first arm is provided with a step portion.
Furthermore, the secondary side of the body is provided with a plurality of grooves. The second partition wall is parallel with the first partition wall. The bobbin comprises a plurality of second pins disposed on the primary side of the body.